The present invention relates to a suspended rail fastening assembly.
European Patent No. EP 0 758 418 B (which corresponds to U.S. Pat. No. 6,079,631) relates to a known railway rail fastening assembly in which the head of the rail is suspended at discrete locations along its length above the rail foundation. As shown in FIG. 1 of the drawings accompanying the present application, in one embodiment of such a known assembly the rail head 100 is supported by means of a pair of elastic members 101 to which a clamping load is applied through respective brackets 102. The desired clamping load is maintained by means of respective wedges 103 inserted between each bracket 102 and an associated upstand or shoulder 104 which is fixed to an underlying rail baseplate 105 secured to a concrete sleeper 106. Such a suspended rail fastening assembly serves to reduce vibration and accordingly is advantageous in an underground railway system, for example. The applicants wish to be able to retrofit such assemblies to existing sleepers. However, this would involve not only dismantling the existing rail fastening assembly, but also lifting the rail. In an underground railway system, where there is little time available for track maintenance work without closing the track, this would be a severe disadvantage.
According to a first aspect of the present invention there is provided a railway rail fastening assembly for suspending a railway rail at discrete locations along its length above a rail foundation, the assembly comprising a pair of elastic members for supporting the head of the rail, a pair of brackets for applying a lateral clamping force to respective ones of the elastic members, a baseplate having first and second shoulders, and a pair of wedge members, each wedge member being inserted between an associated one of the shoulders and an adjacent bracket thereby to maintain the said lateral clamping force, wherein at least one of the said first and second shoulders is removable from the said baseplate and is held in position on the baseplate by the said lateral clamping force.
Thus, since at least one of the shoulders is removable, the baseplate can be slid into position under the rail without the need to lift the rail. Similarly, the baseplate can be removed, if desired, by first removing the or each removable shoulder.
Steel baseplates for use on wooden railway sleepers are sometimes provided with one or more removable shoulders. Such baseplates have apertures in their upper surfaces for receiving the stem of a shoulder, the aperture and/or shoulder stem being configured so as to allow the shoulder to be retained on the baseplate during use whilst permitting easy removal and installation. Such removable shoulders are used in track gauge change applications or other situations where a different type or position of shoulder is required.
Many prior art removable shoulders have a hook-like stem, wider at its widest point than the aperture in the baseplate into which it is to be inserted, such that the shoulder must be rotated as it is being inserted into the aperture, but cannot be removed once installed merely by the application of a vertical force thereto. An alternative form of removable shoulder in a rail fastening assembly is disclosed in the applicants"" British Patent No. GB 1 481 645 B. This type of shoulder has a stem having the shape of an inverted letter T. The stem of the shoulder is inserted into an aperture in the baseplate, the aperture having a widened end so as to accommodate the inverted T-shaped stem. The shoulder is then pushed along the aperture away from the widened end towards the rail, thereby to prevent vertical forces releasing the shoulder. However, in this and similar prior art assemblies the aperture for receiving the stem of the shoulder extends into the rail seat area so as to lie beneath the rail when it is in place.
According to a second aspect of the present invention there is provided a baseplate for use in an assembly embodying the first aspect of the present invention having one removable shoulder, which baseplate comprises a plate having a shoulder fixed on one side of a central area of the plate and an aperture formed in the plate on the other side of the central area of the plate, the aperture extending substantially away from the said central area of the plate, wherein the said aperture is shaped so as to provide, at an end thereof furthest from said central area, locating means for locating a removable shoulder on the said plate. If both shoulders of the assembly are removable, the baseplate comprises a plate having a pair of apertures formed one on each side of a central area of the plate, each aperture extending substantially away from the said central area of the plate, wherein each of the said apertures is shaped so as to provide, at an end thereof furthest from said central area, locating means for locating a removable shoulder on the said plate.
According to a third aspect of the present invention there is provided a removable shoulder for use with an assembly embodying the first aspect of the present invention or a baseplate embodying the second aspect of the present invention, wherein a portion of the shoulder which extends above the baseplate has an upright bearing face against which a lateral force bears, when the shoulder is in use, so as to hold the shoulder in a desired operative position.